Articulated road transport units are known which consist of a tractor vehicle and a semi-trailer. At the level of its rear axle, the tractor vehicle is equipped with a means of coupling it to the semi-trailer. This coupling means is commonly known as an axle tree bolster or fifth wheel.
These tractors have one important and specific feature, by virtue of their particular technical nature and the method of coupling to the semi-trailer. This specific feature condemns them to being coupled solely to semi-trailers to the exclusion of any other type of trailer.
Road transport units are also known which consist of a carrier vehicle which is attached to a trailer. The carrier vehicle has at the rear of its chassis a coupling means known commonly as a towing hook. In this case, the vehicle, carrier and tractor, is a chassis-cab assembly fitted with a body supported by the chassis with which the towing hook is rigid.
Although the range of use of a utility vehicle is already quite vast, the imperatives of profitability of a fleet of utility vehicles require operators to strive for an even greater versatility of use.
Thus, operators want to be able also to use the above-mentioned specific tractors for other particular applications of transport, for example for the transporting of motor vehicles.
With this spirit of profitability in mind and in order to reduce the period of non-availability corresponding to conversion and the fitting of equipment in the workshops run by people who prepare vehicles for specific uses, bodies are known which are removable in the same way as specialised removable structures which are intended to be mounted on bare chassis.
A typical example in the field of vehicle transporters is the removable carrier structure described in the patent filed in ITALY in the name of Messrs. ROLFO under number 53902B/82.
Upon analysis, this prior invention only relates to a simple structure intended to be conventionally connected to a carrier chassis or other chassis, like an immobilised cargo, that is to say like a container fixed by four detachable links to the chassis of the carrier vehicle.
This carrier structure consists essentially of a removable frame intended to be fitted and locked to a simple chassis without giving rise to any functional technical alteration to the carrier vehicle. By way of other technical elements, it comprises only those needed to support the cargo and leaves the towing hook rigid with the chassis so that the carrier vehicle retains its functional individuality. For reasons of ease of manufacture and speed of intervention in the case of a bodywork transplant, the carrier vehicle is not converted.
Due to the weight of this body, the operation of substituting this structure on a given chassis requires the use of external handling means which are not available everywhere, not even on unloading areas.
Therefore, this type of carrier structure comprises no mechanical coupling element other than those which are intended to fix it to the chassis. In particular, it comprises no support for the towing hook which, if it exists, remains rigid with the longitudinal members of the chassis.